An example of known color one-dimensional or line sensors is the one published under 1-232 in the general conference 1985 of the Institute of Electronics and Communication Engineers of Japan. Such line sensor assembly comprises three line sensors encapsulated together, and a glass cap having a red (R), green (G) and blue (B) color filters provided thereon.
The above-mentioned color line sensor assembly has a serious problem in that the three line sensors are disposed side by side and each is associated with a corresponding one of red, green and blue color sensors, and thus the pitch in the longitudinal direction must be relatively large, resulting in a rather poor resolution. Besides, since the device includes three line sensors, an assembling process is required in the course of manufacturing it. Thus, the device is not suitable for mass production and necessitates high cost for production. Further, since the three line sensors must operate synchronously, a complicated driver circuit must be provided for them. There is moreover an additional problem in that the dispersion in the characteristics of the three line sensors can be immediately reflected in the output signal.
It has been conceived that a color line sensor be formed in a single semiconductor integrated circuit chip of the so-called monolithic integrated circuit type which is to be distinguished from one of a hybrid integrated circuit type in which a plurality of active and passive elements are formed on an insulating printed circuit substrate. Such an arrangement allows to achieve a high resolution since it allows to highly compactly arrange the component photoelectric converters.
As a result of their efforts into the study of color line sensors in connection with a single IC chip, the present inventors have determined that the highly compact arrangement of the photoelectric converters causes the following problem: Specifically, the photoelectric converters are formed within a well region formed in the semiconductor substrate in order to improve the spectral sensitivity and to prevent the admixture of excess electric charge. Usually, the well region is electrically isolated from the substate by a PN junction formed with adjacent semiconductor material of the substrate of a different conductivity type therefrom. When a picture element signal is read out from a line (color), crosstalk can appear in the other lines from the read out signal as a result of coupling therebetween via the well region, deteriorating the signal-to-noise (S/N) ratio.